How Spaulding Composites Solved a Defense OEM’s Metal-to-Plastic Conversion Challenge
The Challenge: Converting a High-Impact Structural Part from Metal to Plastic
When a leading Defense Electronics Communications OEM needed to reduce the cost and weight of a critical structural component, the path forward wasn’t straightforward. The part had to withstand high impact and significant wear — conditions that typically favor metal. The challenge wasn’t just finding a plastic material. It was finding the right plastic material that could match or exceed metal’s mechanical performance while delivering meaningful savings in both cost and weight.
This is the kind of problem that separates generalist manufacturers from specialists. Converting a structural part from metal to plastic demands deep expertise in material selection, design for manufacturability, and process engineering — all working together. Get any one of those wrong, and the part fails in the field.
Why Metal to Plastic Conversion Is More Complex Than It Looks
Metal-to-plastic conversion is one of the most misunderstood manufacturing processes. Engineers who approach it as a simple material swap often run into problems: warpage, insufficient impact resistance, premature wear failure, or dimensional instability under load.
For defense applications in particular, the stakes are too high for trial and error. A structural part in communications equipment must perform reliably under demanding field conditions, so the plastic replacement must meet or beat the original metal part across every relevant performance category.
The key variables to address:
Material selection: High-impact and wear-resistant thermoplastics behave very differently from each other. Evaluate lubricity, abrasion resistance, compressive strength, and thermal stability in the context of the specific application.
Part design: Plastic parts are not direct replicas of metal parts. Wall thickness, rib geometry, draft angles, and feature consolidation must all be reconsidered for plastic molding.
Process selection: The manufacturing process — including mold design, gate location, and process parameters — directly affects the mechanical properties of the finished part.
Validation: Lab testing must simulate real-world field conditions. A material that performs well on a datasheet can still underperform in application.
Spaulding Composites’ Engineering Approach
Spaulding Composites’ Applications Engineering team engaged with the Defense OEM early in the project — before final design decisions were locked in. This early collaboration is intentional. Design for manufacturability decisions made upstream have downstream consequences that are far more expensive to fix later.
The team worked through a structured, multi-phase evaluation process:
Phase 1: Broad Material Screening
The team reviewed multiple plastic materials based on their documented high-impact, wear, and lubricity properties. Rather than relying solely on published material data, the team narrowed the candidate list to the materials most likely to meet the specific requirements of this structural application.
Phase 2: Abrasion Testing of Candidate Materials
The team manufactured sample plaques from each prioritized material and subjected them to abrasion testing. This physical testing—not just datasheet comparison—reduced the candidate pool to three materials with the strongest performance profiles for this application.
Phase 3: FEA, Mold Flow Analysis, and Prototype Molding
With three candidate materials identified, Spaulding Composites ran finite element analysis (FEA) and mold flow simulations on each one. The team then built a prototype mold to sample all three materials under actual molding conditions. The team tested sample parts in the laboratory under conditions designed to simulate real-world field use, identifying the top two material candidates.
This combination of simulation and physical testing is critical. Mold flow analysis predicts how a material will fill a tool and where potential defects may form, while FEA predicts how the finished part will respond to structural loads. Neither replaces the other, and neither replaces physical testing of molded parts.
Phase 4: Field Testing and Final Material Selection
The team molded parts using both finalist materials and subjected them to field testing to validate real-world performance. Field testing determined the final material selection — the one that delivered the best balance of structural integrity, wear resistance, and processability in production conditions.
The Results: More Than a Cost and Weight Win
The outcome of this engagement exceeded the original objective. Spaulding Composites’ injection molding and engineering support capabilities delivered:
Successful metal to plastic conversion of the structural part, meeting all performance requirements
Reduced part cost and weight — the primary goals of the program
Improved structural and performance properties compared to the original metal component, not just maintained
Part feature consolidation, reducing total part count by incorporating multiple features into a single molded component
Reduced manufacturing steps and lead times as a result of that consolidation
That last point deserves emphasis. Part consolidation is one of the most underappreciated benefits of a well-executed metal-to-plastic conversion. When multiple features can be designed into a single injection-molded part, the downstream effects — fewer assembly steps, fewer suppliers, shorter lead times, lower total cost — compound significantly.
What Makes This Approach Relevant to Defense Electronics OEMs
Spaulding Composites has decades of experience serving military and defense markets, including aerospace OEMs, Tier 1 suppliers, and defense contractors. That experience matters in metal-to-plastic conversion projects for several reasons:
Material knowledge depth. Defense structural applications require materials with properties that go well beyond what commercial applications need. Understanding which plastics can genuinely replace metal in high-impact, high-wear environments — and how to validate that performance — requires experience that can’t be shortcut.
Mold design and tooling expertise. A rigorous material selection process is only useful if you can reliably manufacture the part. Spaulding’s in-house tooling capabilities allow the engineering team to build and iterate on prototype molds quickly, without the lead time and communication overhead of outsourcing tooling development.
Process engineering integration. The final material is only as good as the process used to mold it. Variations in melt temperature, injection speed, packing pressure, and cooling time all affect the mechanical properties of the finished part. Spaulding Composites’ process engineers work in parallel with materials and design engineers — not in sequence.
Is Metal-to-Plastic Conversion Right for Your Application?
Not every structural part is a candidate for metal-to-plastic conversion. But for components where weight, cost, and lead time are genuine pressures — and where the right engineering partner is involved from the start — the results can substantially outperform the original design.
The questions worth asking:
Does the part need to reduce weight without sacrificing structural performance?
Is part cost a competitive pressure?
Could multiple metal components be consolidated into a single molded part?
Are there features — undercuts, internal channels, complex geometries — that are expensive to machine in metal but feasible to mold in plastic?
If the answer to any of these is yes, a conversation with an applications engineering team is a logical next step.
Talk to Spaulding Composites about your metal-to-plastic conversion project.